Very cool! These old ones have a very unique sound and feel. My '77 Koa Mk I has "Stones" written on the side of the chassis where the HRG or HR would be. It has the 60/100w, Reverb, EQ and multi voltage power xformer. It sounds great. I paid for it but not much more than a used Mk I reissue.
Nice amp my friend. Very clean. Enjoy it!!!